1. Field
The present disclosure relates to an optical member, a backlight unit and a display device, and more particularly to, an optical member achieving high color reproduction accuracy and having high efficiency, and a backlight unit and display device including the same.
2. Background
In recent, a display field has also developed at a fast speed to keep pace with the information age, and a liquid crystal display device (LCD), a plasma display panel device (PDP), an electroluminescence display device (ELD), and a field emission display device (FED) have been accordingly introduced as a flat panel display device (FPD) having advantages in thin thickness, light weight and low power consumption, have quickly replaced a typical cathode ray tubes (CRT) and have taken center stage.
Among others, the LCD is taking center stage as a next-generation display device that enables low power consumption, provides good mobility, is technology-intensive and provides a high added value. In particular, an active matrix LCD (AM-LCD) which includes a thin film transistor capable of regulating power on/off for each pixel and in which pixel electrodes connected to the thin film transistor are arranged in a matrix form is taking center stage due to high resolution and an excellent video reproduction capability.
The LCD includes a liquid crystal display panel including a lower substrate, an upper substrate and a liquid crystal layer between both substrates, and a backlight unit supplying light to the liquid crystal display panel. That is, the LCD is a device in which light is supplied from the backlight unit to the liquid crystal display panel, the transmittance of light is regulated depending on the arrangement of the liquid crystal layer of the liquid crystal display panel, and an image is displayed depending thereon.
The backlight unit includes a light source unit and is divided into an edge type and a direct-lit type depending on the location of the light source unit. The light source unit may be a blue light-emitting diode that generates a blue light. In this case, there is a need for an optical conversion member that may convert the wavelength of incident light and emit converted light. That is, the optical conversion member may convert the blue light into green and red lights and thus, a white light in which the blue light, the green light and the red light are mixed may enter the AM-LCD.
In the case of the edge type, the backlight unit includes a light guide plate, a reflective plate, a light source unit, an optical sheet, an optical conversion member and a bottom casing accommodating them. In this case, the light source unit is disposed on a lateral face of the bottom casing and light enters the lateral face of the light guide plate. The optical conversion member is disposed on the light guide plate and between the light guide plate and the optical sheet.
In the case of the direct-lit type, the backlight unit includes a diffusion plate, a reflective plate, a light source unit, an optical sheet, an optical conversion member and a bottom casing accommodating them. In this case, the light source unit is disposed on the internal top surface of the bottom casing and light enters the rear surface of the light guide plate. The optical conversion member is disposed on the light source unit.
That is, the optical conversion member is disposed on the light guide plate or the light source unit. A portion of light emitted from the light source unit is emitted to the liquid crystal display panel, and a portion of light is recycled to be back reflected and is then emitted back to the liquid crystal display panel. In this case, the light recycled may be re-absorbed by the optical conversion member. Thus, there is a limitation in that light efficiency decreases.
Also, the optical conversion member includes two substrates facing each other and an optical conversion layer that is disposed between the two substrates. That is, there is a limitation in decreasing a thickness because the optical conversion member needs the two substrates disposed on and under the optical conversion layer and the thicknesses of the backlight unit and the AM-LCD increase due to the thicknesses of the substrates.